YAP wrote:
> Hi friends,
> 
> I need to use a 12V SLAB for backup purposes in a design. Normally this
> design is powered but on very rare cases power can be out for 1 hour max
> during which the slab should supply power. It can take months between these
> power outages. I need s simple (hopefully) circuit to keep the slab fully
> charged. With the long time between outages fast charging is not  needed its
> OK if its take a week to charge the battery again after a power outage.
> 
> How would the ***simplest possible*** working charger for a scenario like
> this look like?  I have 12V regulated. I have a PIC so I can measure current
> and voltage and temperature and do PWM. I also have some space left for a
> charger....  Ideas?
> 
> Cheers
> /Ake
To fully charge: charge at approx 1/10 C until terminal voltage = 14.8V
To keep charged: maintain terminal voltage at 13.8V; may require 50 to 
100mA to do so. Depends on capacity, age, temperature, etc.

The above numbers are not hard and fast but should work for a first try.

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